1. Field of the Invention
The present invention relates to a light source apparatus.
2. Description of the Related Art
Conventionally, cold cathode fluorescent lamps (CCFLs) have been used as the light sources of backlight apparatuses for liquid crystal display units. In recent years, however, backlight apparatuses using light emitting diodes (LEDs) as the light sources thereof have become widespread. From the standpoint that LEDs are point light sources, it is necessary to consider, when using the LEDs as the light sources of backlight apparatuses, the arrangement of the LEDs, the diffusion structure of light, the reflection structure of light, or the like to reduce brightness unevenness and color unevenness. Since brightness unevenness and color unevenness are easily caused in backlight apparatuses using LEDs of a plurality of colors such as red, green, and blue colors, consideration is particularly given to the arrangement of the LEDs, the diffusion structure of light, the reflection structure of light, or the like.
Technology to reduce color unevenness caused in a backlight apparatus using LEDs of the three colors of red, green, and blue colors, is disclosed in, for example, Japanese Patent Application Laid-open No. 2008-034361. In the technology disclosed in Japanese Patent Application Laid-open No. 2008-034361, a plurality of types of light emission clusters having the red LEDs thereof arranged in different positions is constituted as light emission clusters in which the LEDs of the three colors described above are arranged in a triangle. Further, the types of the light emission clusters arranged are changed according to the arrangement positions of the light emission clusters.
In addition, there is technology of using LEDs as point light sources and separately controlling the light emission brightness of the LEDs to partially change the brightness of backlight apparatuses and improve the contrast of display images. The control of light emission brightness as described above is generally called local dimming control. In the local dimming control, for each of a plurality of divided regions constituting a screen, the brightness value of an image signal is analyzed and the light emission brightness of corresponding light sources is controlled based on the analysis result of the brightness value. Thus, the contrast of a display image is improved. In addition, by the use of the light sources of a plurality of colors as light sources corresponding to the divided regions, not only the light emission brightness of a backlight apparatus but the colors to be emitted may be changed for each of the divided regions. Specifically, by the change of the ratio of the light emission brightness between the light sources of the plurality of colors, the colors to be emitted from the backlight apparatus may be changed. By the control of the colors to be emitted from the backlight apparatus for each of the divided regions, the color gamut of a display image may be expanded.
Technology to reduce color unevenness caused in a backlight apparatus capable of performing the local dimming control is disclosed in, for example, Japanese Patent Application Laid-open No. 2008-003220. Specifically, Japanese Patent Application Laid-open No. 2008-003220 discloses the technology to reduce color unevenness caused in an outer edge part. In the technology disclosed in Japanese Patent Application Laid-open No. 2008-003220, each of a plurality of light source units (light emission clusters) corresponding to a plurality of divided regions is constituted of a plurality of red, green, and blue LEDs. Further, for each of the light source units, the LEDs are arranged such that the centroid of brightness profiles based on the plurality of red LEDs, the centroid of brightness profiles based on the plurality of green LEDs, and the centroid of brightness profiles based on the plurality of blue LEDs substantially match the centroid of the light source unit.